Rotor current prediction in an electric motor drive having an only-stationary-side compensation network

ABSTRACT

Embodiments of the disclosure provide an electric drive motor system that includes a stationary-side, a rotating-side, and a stationary-side sensor system operable to detect current on the stationary-side and send current-based sensor readings to a controller. The stationary-side further includes a compensation network. The controller is operable to perform a rotor current prediction operation operable to predict a rotor current associated with a rotor of the rotating-side based at least in part on the current-based sensor readings and a parameter of at least one component of the compensation network of the stationary-side.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of an earlier filing date from U.S. Provisional Application Ser. No. 63/333,790 filed Apr. 22, 2022, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

A wound-rotor synchronous machine (WRSM) is an electric motor having a rotor and a stator. The stator is the fixed part of the machine, and the rotor is the rotating part of the machine. The stator usually has a multi-phase winding, and the rotor is made with a field winding instead of permanent magnets. The rotor spins in a magnetic field, and the magnetic field can be produced by the windings or field coils. A field coil is an electromagnet used to generate a magnetic field in an electromagnetic machine, typically a rotating electrical machine such as a motor or generator. It includes a coil of wire through which a current flows. In the case of a machine with field coils, a current must flow in the coils to generate the field, otherwise no power is transferred to or from the rotor. The process of generating a magnetic field by means of an electric current is called excitation. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current.

Conventionally, the rotor winding of a WRSM can be powered or excited using a slip ring and brush assembly systems. However, slip ring and brush assembly systems have disadvantages, including being inefficient at high speeds, frequently requiring maintenance, and being lossy overall, especially at high speeds due to the high contact resistances between the brush and the slip ring.

To avoid the shortcomings of slip ring and brush assembly excitation methods, wireless (or contactless) excitation or wireless power transfer systems or techniques have been developed. In general, wireless power transfer uses various technologies to transmit energy by means of electromagnetic fields (EMFs) without a physical link. In a wireless power transfer system, a transmitter device, driven by electric power from a power source, generates a time-varying EMF, which transmits power via mutual inductance (M) across space to a receiver device. The receiver device uses M to extract power from the EMF and supply the extracted power to an electrical load. Wireless power transfer provides power to electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible. Wireless power techniques mainly fall into two categories, near field and far-field. In near field techniques, the time-varying EMF is generated using a variety of techniques, including resonant inductive coupling. Resonant inductive coupling is the near field wireless transfer of electrical energy between magnetically coupled coils that are part of a resonant circuit tuned to resonate at the same frequency as the driving frequency.

Rotary transformers (RTs) are a type of wireless power transfer system that can be used for the controlled wireless excitation of the rotor windings of a WRSM. An RT performs the same general function as a conventional transformer in that both transfer electrical energy from one circuit to another at the same frequency but different voltages. A conventional transformer works on the principle of electromagnetic induction, i.e., the electromotive force is induced in the closed circuit due to the variable magnetic field around it. An RT differs from a conventional transformer in that the RT geometry is arranged so that the primary windings and the secondary windings can be rotated with respect to each other with negligible changes in the electrical characteristics. In a known configuration, the RT can be constructed by winding the primary and secondary windings into separate halves of a cup core. The concentric halves face each other, with each half mounted to one of the parts that rotate with respect to one another. Magnetic flux provides the coupling from one half of the cup core to the other across an air gap, providing the M that transfers energy from the RT's primary windings to its secondary windings.

Known approaches to using RT systems to provide excitation for a WRSM can include providing the RT system with a resonant tuning network, which is also known as a compensation network. A resonant tuning network can include circuit components (e.g., various combinations of resistors (R), inductors (L), and/or capacitors (C)) that enable the associated transformer to store oscillating electrical energy similar to a resonant circuit and thus function as a band pass filter, allowing frequencies near their resonant frequency to pass from the primary to secondary winding but blocking other frequencies. The amount of M between the primary and the secondary windings, together with the quality factor (Q factor) of the circuit, determines the shape of the frequency response curve. Resonant circuits are often calls LC or LRC circuits because of the inductive, resistive, and capacitive components used to form the resonant circuit. In material science, every material has its own natural frequency. If the external vibration is equal to the natural frequency, resonance occurs. In electrical science, impedance of the inductors and capacitors depends on the frequency. Capacitive impedance is inversely proportional to frequency while inductive impedance is directly proportional to the frequency. At a particular frequency both cancel each other (or tune each other out). Such a circuit is called as resonant circuit, and that particular frequency is resonant frequency. Additionally, for LC circuits, where the reactance of the L component is substantially the same as the reactance of the C component, the L and C components cancel each other out, which means the L and C components compensate each other, or tune each other out.

In conventional RT systems that provide resonant tuning or compensation (i.e., a RT compensation system), the resonant tuning network (or compensation network) is provided on both the stationary (or stator, or primary) side and the rotating (or rotor, or secondary) side of the WRSM. For the primary coil, a basic function of “compensation” is minimizing the input apparent power and/or minimizing the voltage-ampere (VA) rating of the power supply. For the secondary coil, the compensation cancels the leakage inductance of the secondary coil in order to maximize the transfer capability.

RT compensation systems that provide resonant circuit components on both the stationary-side and the rotating-side of the WRSM have shortcomings. For example, it is difficult to place a resonant tuning network or compensation network on the rotating-side due to the very limited space and high-temperature operating conditions on the rotating-side that exceed the temperature rating of commercially available resonant tuning components such as capacitors. Moreover, having a resonant tuning capacitor on the rotating-side decreases mechanical reliability of the rotating part and increases the complexity, mechanical mass, and inertia of the rotating part, especially at high rotational speeds.

For a given torque and speed command in the electric motor, there is a target rotor excitation current that the electric motor drive system needs to inject into the rotor windings. In order to monitor and regulate this rotor winding current, a method of monitoring the actual rotor excitation current is needed so that current regulating systems of the motor can confirm that the target rotor excitation current has been reached and is being maintained. A straightforward approach to monitoring the actual rotor excitation current would be to place one or more current sensors at selected locations on the rotor, then configure the sensors with sufficient electronics (e.g., as Internet of Things (IoT) devices) to transmit readings to current regulating systems on the stationary-side of the motor. However, for many of the same reasons why it is difficult to place a resonant tuning network or compensation network on the rotating-side of a motor, it is also difficult to place a current sensor on a rotating-side of a motor and reliably obtain wired or wireless readings from the current sensor when it is spinning at the same rate (e.g., about 22,000 revolutions per minute (RPM)) and exposed to same high temperatures as the rotor.

Accordingly, there is a need in the art to provide an electric motor drive system having a compensation network and/or rotor current regulation functionality that provide the benefits of compensated RT functionality and/or rotor current sensing without the difficulties associated with providing compensation components and/or rotor current sensors on a rotating-side of an electric motor such as a WFSM.

BRIEF DESCRIPTION OF THE INVENTION

Embodiments of the disclosure provide an electric drive motor system that includes a stationary-side, a rotating-side, and a stationary-side sensor system operable to detect current on the stationary-side and send current-based sensor readings to a controller. The stationary-side further includes a compensation network. The controller is operable to perform a rotor current prediction operation operable to predict a rotor current associated with a rotor of the rotating-side based at least in part on the current-based sensor readings and a parameter of at least one component of the compensation network of the stationary-side.

Embodiments of the disclosure provide a method of fabricating an electric drive motor system that includes forming a stationary-side, a rotating-side, and a stationary-side sensor system operable to detect current on the stationary-side and send current-based sensor readings to a controller. The stationary-side further includes a compensation network. The controller is operable to perform a rotor current prediction operation operable to predict a rotor current associated with a rotor of the rotating-side based at least in part on the current-based sensor readings and a parameter of at least one component of the compensation network of the stationary-side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram illustrating a non-limiting example of an electric drive motor system having a rotor winding prediction module in an only-stationary-side compensation network in accordance with aspects of the disclosure;

FIG. 2 is a simplified block diagram illustrating a non-limiting example of how the electric motor drive system shown in FIG. 1 can be implemented in accordance with aspects of the disclosure;

FIG. 3 is a simplified block diagram illustrating a non-limiting example of how a controller of the electric motor drive system shown in FIG. 1 can be implemented in accordance with aspects of the disclosure;

FIG. 4 is a simplified block diagram illustrating an equivalent circuit representation of the electric drive motor systems shown in FIGS. 1 and 2 ;

FIG. 5 is a simplified block diagram illustrating a further equivalent circuit representation of the electric drive motor systems shown in FIGS. 1 and 2 ;

FIG. 6 is a simplified flow diagram illustrating a methodology in accordance with aspects of the disclosure;

FIG. 7 depicts various equations that can utilized in performing a rotor winding prediction function an electric motor drive system having an only-stationary-side compensation network in accordance with aspects of the disclosure;

FIG. 8 depicts various equations that can utilized in performing a rotor winding prediction function an electric motor drive system having an only-stationary-side compensation network in accordance with aspects of the disclosure;

FIG. 9 depicts various equations that can utilized in performing a rotor winding prediction function an electric motor drive system having an only-stationary-side compensation network in accordance with aspects of the disclosure;

FIG. 10 depicts various equations that can utilized in performing a rotor winding prediction function an electric motor drive system having an only-stationary-side compensation network in accordance with aspects of the disclosure;

FIG. 11 is a simplified flow diagram illustrating a methodology in accordance with aspects of the disclosure;

FIG. 12 is a simplified flow diagram illustrating a methodology in accordance with aspects of the disclosure;

FIG. 13 is a simplified block diagram illustrating an equivalent circuit representation of the electric drive motor systems shown in FIGS. 1 and 2 ;

FIG. 14 is a simplified block diagram illustrating a further equivalent circuit representation of the electric drive motor systems shown in FIGS. 1 and 2 ; and

FIG. 15 is a simplified block diagram illustrating a further equivalent circuit representation of the electric drive motor systems shown in FIGS. 1 and 2 .

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the disclosure provide a novel rotor winding current prediction technique that can be used in an electric motor drive system having a RT compensation system. In some embodiments of the disclosure, the RT compensation system can be an RT having a novel only-stationary-side compensation network. The electric motor drive system can include an electric motor (e.g., a WRSM) having a stationary-side and a rotating-side. The novel rotor winding current prediction technique and/or the novel only-stationary-side compensation network disclosed herein addresses the previously-described difficulties associated with placing a rotor winding current sensor and/or a compensation network on the rotating/secondary side. The novel rotor winding prediction technique is configured and arranged to eliminate the need for current sensing and sensor output communications on the rotating-side, and the only-stationary-side compensation network is configured and arranged to eliminate the need for compensation components on the rotating-side. In some embodiments of the invention, the only-stationary side compensation network can be implemented as an only-stationary-side resonant LCC (inductor-capacitor-capacitor) network operable to provide tuning only on the stationary-side (or primary side) and no compensation elements (e.g., no resonant tuning capacitor element(s)) on the rotational side (or secondary side) for RT compensation system applications. In embodiments described herein, the terms “only-stationary-side” applied to a compensation network implemented in an electric driver motor system having a stationary-side and a rotating-side means that no compensation components are provided on the rotating side.

In aspects of the disclosure, the previously-described electric motor drive system includes a resonant inverter operable to convert direct current (DC) (e.g., received from a vehicle battery) to high frequency (HF) AC and provide the HF AC to the only-stationary-side resonant LCC network to wirelessly provide excitation AC to rotor excitation windings. A rotor rectifier converts the excitation AC to DC excitation and provides the same to rotor windings of the electric motor. The novel rotor winding current prediction technique leverages features of the only-stationary-side resonant LCC to enable the rotor winding current to be estimated based at least in part on the measurement and analysis of the current generated by the resonant inverter. Embodiments of the disclosure use a stationary-side sensor system (e.g., one or more IoT sensors) to provide a measurement of the AC excitation current generated by the resonant inverter to a controller operable to apply a novel winding current prediction technique that predicts the rotor winding current based on a function (e.g., f(C₁, C_(f1), L_(f1), L_(m), L_(s1) shown in FIG. 3 ) of the AC excitation current plus other parameters of the electric motor drive system.

The only-stationary-side resonant LCC is designed using a novel design methodology that includes computing the “reflected” stationary-side coil impedance that is due to the impedance on the rotating-side coil of the electric motor. In general, a reflected impedance (or inductance) is the part of the impedance of a circuit (e.g., circuit A) that is due to the influence another coupled circuit (e.g., circuit B). The novel design methodology further includes selecting the location and component values of the only-stationary-side resonant LCC network such that the only-stationary-side resonant LCC network tunes the “reflected” stationary-side coil impedance that is due to the impedance on the rotating-side coil out of the only-stationary-side resonant LCC network. For example, with an appropriate location and sizing of a capacitive component of the only-stationary-side resonant LCC network, the rotating-side windings of the electric motor can be tuned from the stationary-side through the appropriate location and sizing of the capacitive component (e.g., the C₁ capacitor shown in FIG. 2 ) of the only-stationary-side resonant LCC tuning network.

With the only-stationary-side resonant LCC network configuration, the primary-side coil acts as a load-independent and coupling-factor-independent constant current source. With this property of the only-stationary-side resonant LCC network, the primary-coil current does not depend on the rotor current or relative position of the primary and secondary coils. As a result, the inverter output current's root mean square (RMS) value (which would have active and reactive components) is directly related to the output current of the only-stationary-side resonant LCC network. In the disclosed configuration of the electric motor drive system, no secondary-side compensation network is used or needed. With the high-coupling factor and large L_(rotor) inductance, the need for a tuning network is eliminated. The L₂ inductance can be referred to the primary-side, and with a proper design and sizing of the C₁ capacitor (shown in FIG. 2 ), the secondary-winding can be tuned from the primary-side. This configuration of the electric motor drive system is also insensitive to the L_(rotor) inductance (shown in FIG. 2 ) because the rotor winding inductance is on the DC side of the electric motor (i.e., downstream from the rotor-side rectifier 210 shown in FIG. 2 ), and inductors in steady-state operate as a short-circuit under DC voltages and currents. Thus, the L_(rotor) inductance only introduces a time-constant when the current changes from one value to another. Other than introducing a time constant (inertia to the change of the current), this inductance is not reflected to the rectifier input and to the primary-side. Accordingly, the novel rotor winding current prediction technique is operable to predict the rotor current by deriving the rotor current as a function of the other stationary-side system parameters and the inverter output current, which is easy to measure from the stationary-side, easy to process, and easy to control. Additionally, because the LCC tuning on the primary-side is configured and arranged such that no compensation (e.g., no resonant tuning capacitor(s)) is on secondary-side, the tuning circuitry on secondary-side is simplified (i.e., the only tuning element on the secondary-side is the secondary windings), the need to identify and provide a high-temperature rotating-side capacitor is eliminated, the cost associated with secondary-side tuning components is eliminated, and the overall reliability of the wireless motor excitation system is improved.

Turning now to a more detailed description of embodiments of the disclosure, FIG. 1 depicts a system 100 embodying aspects of the disclosure. The system 100 includes an energy source 110 electronically coupled to an electric motor drive system 102. The electronic motor drive system 102 includes a resonant inverter 120, a DC excited motor 130, and a controller 150, configured and arranged as shown. In accordance with aspects of the disclosure, the DC excited motor 130 includes an only-stationary-side compensation network 140 and a network of one or more stationary-side sensors 170. Further in accordance with aspects of the disclosure, the controller 150 includes a rotor winding current prediction module 160. Although the resonant inverter 120, the DC excited motor 130, the only-stationary-side compensation network 140, and the controller 150 are depicted as separate components, it is understood that the resonant inverter 120, the DC excited motor 130, the only-stationary-side compensation network 140, and the controller 150 can be configured and arranged in any suitable combination. For example, the controller 150 can be incorporated within the resonant inverter 120; the resonant inverter 120 can be incorporated within the DC excited motor 130; and/or the resonant inverter 120 and the controller 150 can be incorporated within the DC excited motor 130.

The energy source 110 can be implemented in a variety of forms, including, for example as a battery. In some embodiments of the disclosure, the battery can be a battery pack having a set of one or more individual battery cells connected in series or in parallel and that operate under the control of one or more controllers, such as a battery control module (BCM) that monitors and controls the performance of the battery pack. The BCM can monitor several battery pack level characteristics such as pack current measured by a current sensor, pack voltage, and pack temperature, for example. The battery pack can be recharged by an external power source (not shown). The battery pack can include power conversion electronics operable to condition the power from the external power source to provide the proper voltage and current levels to the battery pack. The individual battery cells within a battery pack can be constructed from a variety of chemical formulations. Battery pack chemistries can include, but are not limited, to lead acid, nickel cadmium (NiCd), nickel-metal hydride (NIMH), lithium-ion or lithium-ion polymer.

The resonant inverter 120 is electrically coupled between the energy source 110 and the DC excited motor 130 to transfer excitation energy from the energy source 110 to the DC excited motor 130. More specifically, the resonant inverter 120 is operable to provide energy from the energy source 110 to the only-stationary-side compensation network 140 of the DC excited motor 130 at a desired resonant frequency for purposes of providing excitation to the DC excited motor 130. In embodiments of the disclosure, the resonant inverter 120 is operable to convert the DC voltage from the energy source 110 to AC current at the desired resonant frequency as required by the DC excited motor 130 and the only-stationary-side compensation network 140 for motor excitation. In embodiments of the disclosure, the resonant inverter 120 can be a full-bridge resonant inverter having four switches organized as two “phase legs.” Each phase leg can include two switches connected in series and between a positive DC rail and a negative DC rail. A phase node can be positioned between the two switches of each phase leg to provide the phases of an AC waveform output at a desired resonant frequency. In some embodiments of the disclosure, the resonant inverter 120 generates HF AC. The controller 150 is electronically coupled to the phase leg switches to control the on/off states of the switches, thereby controlling the frequency and phase of the AC waveform generated by the resonant inverter 120. The controller 150 includes a computing device (with memory), which includes a computer, a microprocessor, a digital signal processor, and the like, configured and operable to execute software commands and programs, and which can include associated firmware, such that the controller 150 is configured and operable to control the on/off switching operations of the resonant inverter 120.

The controller 150 is also configured to send various control commands to the DC excited motor 130 to control, for example, torque and/or speed of the motor 130. In order to provide accurate control commands, the controller 150 must be able to monitor the status of the current (e.g., I_(rotor)) into the rotor windings of the motor 130. A straightforward approach to monitoring the actual rotor winding current would be to place one or more current sensors at selected locations on the rotor, then configure the sensors with sufficient electronics (e.g., as IoT devices) to transmit readings to current regulating systems of the controller 150. However, for many of the same reasons why it is difficult to place a resonant tuning network or compensation network on the rotating-side of the motor 130, it is also difficult to place a current sensor on a rotating-side of a motor 130 and reliably obtain wired or wireless readings from a current sensor that is spinning at the same rate (e.g., about 22,000 RPM)) and that is exposed to same high temperatures as the rotor of the motor 130. To address this issue, embodiments of the disclosure configure the controller 150 to include a rotor winding current prediction module 160. In accordance with aspects of the disclosure, the controller 150 receives inverter output current/voltage readings (e.g., I_(inv_o), V_(inv_o) shown in FIG. 2 ) from the stationary-side sensor(s) 170, and uses the same, along with other parameters of the system 100, to predict the rotor winding current without having to directly measure the rotor winding current. Additional details of the controller 150 and the rotor winding current prediction module 160 are illustrated in FIGS. 2-10 and described in greater detail subsequently herein.

The DC excited motor 130 can be any eclectic motor design that is suitable for the work to be performed by the motor. Examples of work that can be done by motors in conventional automobile-based motor applications include operating or moving power windows; power seats; fans for the heater and the radiator; windshield wipers; and/or the engine of a vehicle having a hybrid-electric vehicle configuration. Regardless of the type of the DC excited motor 130, it relies on electromagnetism and flipping magnetic fields to generate mechanical power. A conventional implementation of the DC excited motor 130 includes five basic parts, namely, a stator; a rotor; a solid axle; coils; and a so-called “squirrel cage.” The winding of the stator in a DC excited motor is a ring of electromagnets that are paired up and energized in sequence, which creates the rotating magnetic field. The rotor in a DC excited motor does not have any direct connection to a power source, and it does not have brushes. Instead, it often uses the previously-described squirrel cage. The squirrel cage in a DC excited motor is a set of rotor bars connected to two rings, one at either end. The squirrel cage rotor goes inside the stator. When excitation power is sent through the stator, it creates an EMF. The bars in the squirrel cage rotor are conductors, so they respond to the flipping of the stator's poles, which rotates the rotor and creates its own magnetic field. The key to an induction motor, where the field of the rotor is induced by the field of the stator, is that the rotor is always trying to catch up. It is always looking for stasis, so it is rotating to find that steady state. However, the EMF produced by the stator is always going to be a little faster than the rotor's field. The spin of the rotor is creating the torque needed to create mechanical power to turn the wheels of a car or the blades of a fan. Some DC excited motors use a wound rotor (e.g., a WRSM), which is wrapped with wire instead of being a squirrel cage. In either case, there is only one moving part in a DC excited motor, which means there are fewer things that need to be replaced or maintained.

In some embodiments of the disclosure, the DC excited motor 130 can be a WRSM. A WRSM is a rotating electric motor having a rotor and a stator. The stator is the fixed part of the machine, and the rotor is the rotating part of the machine. The stator usually has a multi-phase winding, and the rotor is made with a field winding instead of permanent magnets. The rotor spins in a magnetic field, and the magnetic field can be produced by the windings or field coils. In the case of a machine with field coils, an excitation current must flow in the coils to generate the field, otherwise no power is transferred to or from the rotor. Field coils yield the most flexible form of magnetic flux regulation and de-regulation, but at the expense of a flow of electric current. Conventionally, the rotor winding of a WRSM can be powered or excited with a slip ring and brush assembly. However, slip ring and brush systems have disadvantages, including being inefficient at high speeds, frequently requiring maintenance, and being lossy overall, especially at high speeds due to the high contact resistances between the brush and the slip ring systems.

To avoid the shortcomings of slip ring and brush assembly excitation methods, the only-stationary-side compensation network 140 is incorporated within a RT compensation system (not shown separately from the motor 130) operable to provide compensated wireless excitation or wireless power transfer from a stator-side of the motor 130 to a rotor-side of the motor 130. In embodiments of the disclosure, the only-stationary-side compensation network 140 can be implemented as a specially designed only-stationary-side RT compensation system. In general, the RT is a circuit and method for wireless power transfer to the rotor windings of a WRSM for controlled excitation. An RT is essentially the same as a conventional transformer in that it transfers electrical energy from one circuit to another at the same frequency but different voltage. In general, a conventional transformer works on the principle of electromagnetic induction, i.e., the electromotive force is induced in the closed circuit due to the variable magnetic field around it. An RT differs from a conventional transformer in that the RT's geometry is arranged so that the primary windings and secondary windings can be rotated with respect to each other with negligible changes in the electrical characteristics. In a known configuration, the RT can be constructed by winding the primary and secondary windings into separate halves of a cup core. The concentric halves face each other, with each half mounted to one of the parts that rotate with respect to one another. Magnetic flux provides the coupling from one half of the cup core to the other across an air gap, providing the M that couples energy from the RT's primary windings to its secondary windings.

In conventional RT designs that provide resonant tuning or compensation (i.e., a RT compensation system), a resonant tuning network (or compensation network) is provided on both the stationary (or primary) side and the rotating (or secondary) side of the WRSM. RT designs that have resonant circuit components on both the stationary-side and the rotating-side of the WRSM are difficult to implement. For example, it is difficult to, in practice, place a resonant tuning network or compensation circuitry on the secondary-side due to very limited rotor space and the high-temperature rotor operating conditions that exceed the temperature rating of commercially available compact capacitors. Moreover, having a resonant tuning capacitor on the secondary-side increases the complexity of the rotating part, increases the mechanical mass, increases the inertia, and reduces mechanical reliability, especially at high rotational speeds.

The only-stationary-side compensation network 140 addresses the difficulties associated with going beyond on-paper designs and computer simulations and actually implementing (i.e., building and using) conventional RT compensation system designs that include stationary-side and rotating-side compensation networks by providing the benefits of compensated RT functionality without the difficulties associated with providing compensation circuitry on a rotating-side of a DC excited motor 130 (e.g., a WFSM). More specifically, the only-stationary-side compensation network 140 is operable to assist with the delivery of rotor excitation current from the stationary-side to the rotating rotor wirelessly, thereby eliminating the brush and slip ring maintenance issues, as well as the inefficiencies, fabrication challenges, and design drawbacks associated with brush and slip ring systems.

In aspects of the disclosure, the only-stationary-side compensation network 140 accounts for having no resonant tuning capacitor on the secondary side by providing an extra resonant tuning capacitor (i.e., one of the resonant tuning capacitors of an LCC network implementation of the only-stationary-side compensation network 140) on the primary side and adjusting the two primary side resonant tuning capacitors so that the uncompensated secondary side doesn't impose inefficiencies or other drawbacks on the network 140. In embodiments of the disclosure, an only-stationary-side LCC design methodology is provided that includes reflecting the impendence and/or inductance of the secondary side to the primary side, and the leakage inductance of this secondary coil (e.g., L₂ shown in FIG. 2 ) is tuned on the primary side. In general, a reflected impedance (or inductance) is the part of the impedance of a circuit (e.g., circuit A) that is due to the influence another coupled circuit (e.g., circuit B). In embodiments of the disclosure, this can be accomplished by deriving the equivalent circuit models of the system 100, as well as the overall impedance model of the system 100, which allows the reflective impedance from the secondary to the primary to be computed. A further simplification is applied to the derived equivalent circuit models so the overall impedance seen by the resonant inverter 120 can be calculated. In order to tune this overall impedance to a unity power factor, a tuning capacitor (e.g., C₁ shown in FIG. 2 ) of the LCC design is recalculated. Thus, the only-stationary-side compensation network 140 eliminates the need for capacitor tuning on secondary side, and the need for a secondary side resonant tuning capacitor(s) and tuning thereof, by providing additional primary side tuning components (e.g., a resonant tuning capacitor(s)) and adjusting the values of the tuning components on the primary side. Additional details of the only-stationary-side LCC design and its associated design methodology in accordance with aspects of the disclosure are illustrated in FIGS. 2 and 11-15 and described subsequently herein.

FIG. 2 depicts a system 100A having a vehicle battery 110A electronically coupled through a DC-link capacitor (C_(dc)) to an electric motor drive system 102A. The system 100A is a non-limiting example implementation of the system 100 (shown in FIG. 1 ); the vehicle battery 110A is a non-limiting example implementation of the energy source 110 (shown in FIG. 1 ); and the electric motor drive system 102A is a non-limiting example implementation of the electric motor drive system 102 (shown in FIG. 1 ). The electric motor drive system 102A can be implemented as a resonant inverter 120A electronically coupled to the controller 150 and a simplified representation of an electric machine 130A. The resonant inverter 120A is a non-limiting example implementation of the inverter 120 (shown in FIG. 1 ). The controller 150 is operable to include the rotor winding current prediction module 160. The electric machine 130A is an example implementation of the DC excited motor 130 (shown in FIG. 1 ). The electric machine 130A includes a novel only-stationary-side resonant LCC 140A, a network of one or more sensors 170 (e.g., IoT devices), stationary-side excitation windings L₁, rotating-side excitation windings L₂, a rectifier 210, and a rotor element represented by a rotor inductance L_(rotor) and a rotor resistance R_(rotor). The novel only-stationary-side resonant LCC 140A is a non-limiting example implementation of the novel only-stationary-side compensation network 140 (shown in FIG. 1 ). The system 100A includes a stationary-side (e.g., stator-side) 220 and a rotating-side (e.g., a rotor-side) 230. In general, the stationary-side 220 includes the stator windings L₁ and the circuit elements to the left thereof, and the rotating-side 230 include the stator windings L₂ and the circuit elements to the right thereof. Although the resonant inverter 120A, the electric machine 130A, and the controller 150 are depicted as separate components, it is understood that the resonant inverter 120A, the electric machine 130A, and the controller 150 can be configured and arranged in any suitable combination of components. For example, the controller 150 can be incorporated within the resonant inverter 120A; the resonant inverter 120A can be incorporated within the electric machine 130A; and/or the resonant inverter 120A and the controller 150 can be incorporated within the electric machine 130A.

Referring still to FIG. 2 , the stationary-side 220 is configured to transfer power to the rotating-side 230 using inductive power transfer, and the rotating-side 230 is configured to receive power via inductive power transfer from the stationary-side 220. The stationary-side 220 includes a DC vehicle battery 110A, a DC link capacitor C_(dc), a resonant inverter 120A, the only-stationary-side resonant LCC 140A, and the stator-side coil L₁. The resonant inverter 120A receives a DC input signal from the vehicle batter 110A and converts the DC input signal to an AC output signal at a desired resonant frequency. In some embodiments of the disclosure, the resonant inverter 120A is a full bridge inverter circuit operable to include four power electronics switching devices T₁, T₂, T₃, T₄, configured and arranged as shown. The switching devices T₁, T₂, T₃, T₄ can be implemented in any suitable format, including but not limited to, metal oxide semiconductor field effect transistors (MOSFETs), BJTs, FETs, IGBTs, IGFETs, and the like. The controller 150 is electrically coupled to each of the switching devices T₁, T₂, T₃, T₄ to control the switching operation of the resonant inverter 120A. The controller 150 turns the switching devices T₁, T₂, T₃, T₄ on and off to generate the AC output signal V_(inv_out) at the desired resonant frequency. The controller 150 includes a computing device (with memory), which includes a computer, a microprocessor, a digital signal processor, and the like, configured and operable to execute software commands and programs, and which can include associated firmware, such that the controller is configured and operable to control the on/off switching operations of the resonant inverter 120A.

The controller 150 is also configured to send various control commands to the DC excited motor 130A to control, for example, torque and/or speed of the motor 130A. In order to provide accurate control commands, the controller must be able to monitor the status of the current into the rotor windings L_(rotor) of the motor 130A. A straightforward approach to monitoring the actual current into the rotor winding L_(rotor) would be to place one or more current sensors at selected locations on the rotor, then configure the sensors with sufficient electronics (e.g., as IoT devices) to transmit readings to current regulating systems of the controller 150. However, for many of the same reasons why it is difficult to place a resonant tuning network or compensation network on the rotating-side 230 of the motor 130A, it is also difficult to place a current sensor on a rotating-side 230 of a motor 130A and reliably obtain wired or wireless readings from a current sensor that is spinning at the same rate (e.g., about 22,000 RPM)) and that is exposed to same high temperatures as the rotor of the motor 130A. To address this issue, the controller 150 is operable to include a rotor winding current prediction module 160. In accordance with aspects of the disclosure, the controller 150 receives inverter output current/voltage readings (I_(inv_out), V_(inv_out)) from the stationary-side sensor(s) 170, and uses the same, along with other parameters of the system 100A, to predict the rotor winding current I_(rotor) without having to directly measure the rotor winding current I_(rotor). Additional details of the controller 150 and the rotor winding current prediction module 160 are illustrated in FIGS. 3-10 and described in greater detail subsequently herein.

The only-stationary-side resonant LCC 140A interconnects the resonant inverter 120A with the stator-side coil L₁. In the non-limiting example embodiment of the disclosure depicted in FIG. 2 , the only-stationary-side resonant LCC 140A is configured to include a stator-side inductor L_(f1), a stator-side series capacitor C₁, (in series with the stator-side coil L₁) and a stator-side parallel capacitor C_(f1) (in parallel with the stator-side inductor L_(f1)). The stator-side series capacitor C₁ is serially coupled to a positive terminal of the stator-side coil L₁, and the stator-side parallel capacitor C_(f1) is coupled in parallel with the stator-side coil L₁.

The rotating-side 230 includes a rotor-side coil L₂ electrically coupled to a rectifier 210. The rotor-side coil L₂ is sufficiently close to the stator-side coil L₁ to be within an EMF generated by the stator-side coil L₁ such that M is between the stator-side coil L₁ and the rotor-side coil L₂. The rotor-side coil L₂ uses M to generate an AC current, and the rectifier 210 converts the AC current to a DC current (Irotor). In some embodiments of the disclosure, the rectifier 210 is a bridge rectifier circuit includes four diodes D₁, D₂, D₃, D₄. The DC current is provided to a rotor of the electric machine 130A. The rotor is represented in FIG. 2 as the inductor L_(rotor) in series with the resistor R_(rotor).

Energy is transferred through the M between the stator-side coil L₁ and the rotor-side coil L₂, any L₁/L₂ leakage inductance does not have a direct contribution to the active power transfer. Leakage inductance can be further undesirable because it causes the voltage to change with loading. In conventional approaches to decreasing leakage inductance and increasing M, a rotor-side compensation circuit (e.g., a rotor-side capacitive circuit/element) is provided on the rotating-side 230. However, for applications such as the system 100, 100A where the rotor-side rotates with respect to the stator-side, it is extremely difficult to fabricate a rotor having a rotor-side compensation circuit. Embodiments of the disclosure avoid the need for the rotor-side compensation circuit/element by configuring and arranging the only-stationary-side resonant LCC 140A such that compensation that would in conventional RT compensation designs be provided by a rotor-side compensation circuit/element on the rotating-side 230 is instead provided by the design and component values settings of the only-stationary-side resonant LCC 140A. Additional details of the only-stationary-side resonant LCC 140A design and its associated design methodology in accordance with aspects of the disclosure are illustrated in FIGS. 3-15 and described subsequently herein.

FIG. 3 depicts additional details of how the controller 150 can be implemented as a current/voltage controller 150A having a rotor winding current prediction module 160A and a current/voltage regulation module 320. The controller 150A is also configured to send various control commands to the DC excited motor 130A to control, for example, torque and/or speed of the motor 130A. In order to provide accurate control commands, the controller must be able to monitor the status of the current I_(rotor) into the rotor windings L_(rotor) of the motor 130A. To avoid the difficulties associated with placing a current sensor on a rotating-side of the motor 130A and reliably obtain wired or wireless readings from a current sensor that is spinning at the same rate (e.g., about 22,000 RPM)) and that is exposed to same high temperatures as the rotor of the motor 130A, the controller 150A is operable to include the rotor winding current prediction module 160A. In accordance with aspects of the disclosure, the controller 150A receives inverter output current/voltage readings from the stationary-side sensor(s) 170, and uses the same, along with other parameters of the system 100A (f(C₁, C_(f1), L_(f1), L_(m), L_(s1)) 310), to predict the rotor winding current without having to directly measure the rotor winding current.

The rotor winding current prediction module 160 leverages features of the only-stationary-side resonant LCC 140A to enable the rotor winding current I_(rotor) to be estimated based at least in part on the measurement and analysis of the current I_(inv_out) generated by the resonant inverter. With the configuration of the only-stationary-side resonant LCC network 140A, the primary-side coil L₁ acts as a load-independent and coupling-factor-independent constant current source. With this property of the only-stationary-side resonant LCC network 140A, the primary-coil current does not depend on the rotor current or relative position of the primary and secondary coils L₁, L₂. As a result, the RMS value (which would have active and reactive components) of the inverter output current I_(inv_out) is directly related to the output current of the only-stationary-side resonant LCC network 140A. In the disclosed configuration of the electric motor drive system 100, 100A, no secondary-side compensation network is used or needed. With the high-coupling factor and large L_(rotor) inductance, the need for a tuning network is eliminated. The L₂ inductance can be referred to the primary-side and with a proper design and sizing of the C₁ capacitor, the secondary-winding can be tuned from the stationary (or primary) side 220. This configuration of the electric motor drive system 102A is also insensitive to the L_(rotor) inductance because this rotor winding inductance is on the DC side of the electric motor 130A, and inductors in steady-state operate as a short-circuit under DC voltages and currents. Thus, this inductor (L_(rotor)) only introduces a time-constant when the current changes from one value to another. Other than introducing a time constant (inertia to the change of the current), this inductance is not reflected to the rectifier input and to the primary-side. Accordingly, the novel rotor winding current prediction module 160, 160A is operable to predict the rotor current L_(rotor) by deriving the rotor current L_(rotor) as a function of the other system parameters and the inverter output current I_(inv_out), which is easy to measure from the stationary-side, easy to process, and easy to control.

A non-limiting example of how the functionality of the controller 150A and the rotor winding current prediction module 160A are illustrated in FIGS. 4-10 and described in greater detail subsequently herein. The diagrams and equations depicted in FIGS. 4-10 are provided as a non-limiting implementation example. Accordingly, some well known details associated with the equations are mentioned briefly or not provided in the interest of brevity. Turning first to FIG. 4 , in order to analyze the circuitry of the system 100A in FIG. 2 , a coupled inductor model 100B of the primary and secondary-side windings L₁, L₂ can be used with the self-inductances and the leakage inductances of each side 220, 230, as well as the coupling factor. The parameters of the coupled inductor model 100B of the rotor transformer windings L₁, L₂ are defined as follows: L₁: Primary-side self-inductance; L_(m): Mutual inductance; L_(s1): Primary-side leakage inductance; L₂: Secondary-side self-inductance; L_(s2): Secondary-side leakage inductance L_(s2): Secondary leakage inductance referred to the primary-side; and n: Number of turns, n₁/n₂. For each side of the transformer, self-inductance is equal to the leakage inductance plus the magnetizing inductance. Therefore, Equation-1 through Equation-8 shown in FIG. 7 can be written. The rectifier output resistance (or rotor winding resistance) can be referred to (or reflected to) the rectifier input with an equivalent load resistance R_(L) that is given by Equation-9 (shown in FIG. 8 ). When this resistance R_(L) is used with the coupled inductor model 100B, the turns ratio between the turns should be taken into account as depicted by Equation-10 (shown in FIG. 8 ), where R_(L) is the load resistance referred to (or reflected to) the rectifier input; and R′_(L) is the equivalent load resistance referred to (or reflected to) the stationary (or primary) side 220.

With the above inductance and load resistance definitions, the circuit diagram of the system 100A (i.e., the electric motor drive system 102A) can now be redrawn as the system 100C shown in FIG. 5 . As shown in FIG. 5 , the rotor current I′_(RL) is the difference between the two branch currents as given by Equation-11 (shown in FIG. 8 ). Because I_(Cf1)=U_(Cf1)×jωC_(f1) and I_(m)=U_(m)/(jωL_(m)), then the rotor current can be rewritten as Equation-12 (shown in FIG. 8 ). Here, U_(m) would be equal to the U_(Cf1) voltage plus the voltage drop across the branch that includes C₁ and L_(s1). Therefore, Equation-13 and Equation-14 (shown in FIG. 8 ) can be generated. Here, I_(Cf1) can be substituted with U_(Cf1)×jωC_(f1) to generate Equation-15 (shown in FIG. 8 ).

As shown in FIG. 5 , the U_(Cf1) voltage can be written as a function of inverter output voltage minus the voltage drop across the tuning inductor L_(f1), which is given by Equation-16 (shown in FIG. 9 ). With this substitution, U_(m) can be expressed by Equation-17 (shown in FIG. 9 ). Because U_(m)/jωL_(m) is needed for the magnetizing branch, Equation-18 (shown in FIG. 9 ) can be generated. With U_(m)/jωL_(m) generated, the rotor current can be rewritten as shown in Equation-19 (shown in FIG. 9 ). U_(m)/jωL_(m) and U_(CF1)=V_(inv0)−I_(inv0)×jωL_(m) can be substituted as shown in Equation-20, Equation-21, and Equation-22 (shown in FIG. 10 ). Finally, the rotor current is given by Equation-23 (shown in FIG. 10 ) and/or Equation-24 (shown in FIG. 10 ).

From the example depicted in FIGS. 4-10 , it can be seed that I_(R) is expressed as a function of in and other parameters. In the disclosed representation, the prediction of the rotor current has no dependency on the rotor winding resistance or inductance, and there is no dependency on output voltage. While there is a dependency on the inverter output voltage (that would change with the inverter duty cycle or inverter input voltage), the increase or decrease of rotor current and inverter output current are linearly proportional. Therefore, the disclosed rotor current prediction has no sensitivity to the inverter input or output voltage and it has no sensitivity to the inverter duty cycle changes. I_(R′) _(L) can be controlled from the resonant network input side (inverter output). The relationship between the I_(R′) _(L) and I_(inv) _(o) is linear. Therefore, the I_(R′) _(L) can be approximated to a linear equation that uses the inverter output voltage to predict the rotor current. Because the rotational (or rotor) side 230 is an equivalent resistive-inductive load, the rotor current prediction algorithm uses a compensation computation for improved accuracy. The equations depicted in FIGS. 1-10 use the first harmonic approximation for the inverter output voltage and current. Embodiments of the disclosure also cover implementing a compensation approach to account for the voltage and current harmonics at the inverter output voltage and current.

FIG. 6 depicts a more general methodology 600 illustrating how the functionality of the controller 150A and the rotor winding current prediction module 160A can be implemented in accordance with embodiments of the disclosure. The methodology 600 begins at block 602 where the rotor current is made equal to the inverter output current minus the parallel tuning capacitor current minus the magnetizing branch current. At block 604, the parallel tuning capacitor is written as a function of the branch voltage; and the magnetizing current as written as a function of the branch voltage. In block 606, the magnetizing branch voltage is set equal to the parallel tuning capacitor voltage plus the voltage drop across the series tuning capacitor plus the voltage drop across the primary leakage inductance. At block 608, the parallel tuning capacitor current is substituted with its voltage equation. At block 610, the parallel tuning capacitor voltage is made equal to the inverter output voltage less the voltage drop across the series tuning inductor. At block 612, the obtained equation is converted in terms of the series tuning inductor current. At block 604, the rotor current is extracted in terms of the inverter output current and other parameters/values (e.g., f(C₁, C_(f1), L_(f1), L_(m), L_(s1))).

FIG. 11 depicts a flow diagram illustrating a methodology 1100 that can be performed by the system 100, 100A (shown in FIGS. 1 and 2 ). In some embodiments of the invention, portions of the methodology 1100 (e.g., blocks 1112, 1114) can optionally be performed by a computer aided design (CAD) system running on a processor (e.g., having the same processor functionality as the controller 150) operable to perform computations, circuit modeling, and circuit simulation operations that can optionally be used to select the compensation component values of the only-stationary-side resonant LCC 140A. In accordance with aspects of the disclosure, the previously-described CAD system can be implemented using CAD software applications operable to optionally perform the various computations and algorithms illustrated and described in FIGS. 11-15 . Although the description of the methodology 1100 makes reference to components of the system 100A, the description applies equally to the corresponding element(s) of the system 100.

As shown in FIG. 11 , the methodology 1100 begins at block 1102 by generating AC. In embodiments of the disclosure, the AC can be HF AC generated by using the resonant inverter 120A to convert DC received from the vehicle battery 110A to the HF AC. At block 1104, the HF AC is received at the novel only-stationary-side compensation/tuning network (e.g., the only-stationary-side resonant LCC 140A) associated with the primary coils L1.

Blocks 1112 and 1114 are offline operations that can be used to design the only-stationary-side tuning network (e.g., the only-stationary-side resonant LCC 140A) used at blocks 1104, 1106. At block 1112, the “reflected” stationary-side coil impedance that is due to the impedance on the rotating-side coil is computed. In some embodiments of the invention, impedance associated with the rotating-side or primary coils is reflected to the stationary-side. In some embodiments of the invention, the impedances associated with the primary coils and the load (as represented by L_(rotor) and R_(rotor) in FIG. 2 ) are reflected to the stationary-side. At block 1114, the location and components values of the only-stationary-side tuning network are selected such that the only-stationary-side tuning network tunes the “reflected” stationary-side coil impedance that is due to the impedance on the rotating-side coil out of the only-stationary-side tuning network. For example, with an appropriate location and sizing of a capacitive component (e.g., the C₁ capacitor) of the only-stationary-side tuning network, the rotating-side winding (e.g., L₂) can be tuned from the stationary-side through the appropriate location and sizing of the capacitive component (e.g., the C₁ capacitor) of the only-stationary-side tuning network. Additional details of how blocks 1112 and 1114 can be implemented are depicted in FIGS. 12-15 and described in greater detail subsequently herein.

Subsequent to the operations at block 1104, the methodology 1100 moves to block 1106. At block 1106, the only-stationary-side tuning network design has compensation components (e.g., including the two capacitive elements C₁, C_(f1)) that enable the only-stationary-side tuning network to act as a load, and further act as an M-independent, constant current source operable to use the AC received at block 1104 to generate an alternating EMF. With this property of the only-stationary-side tuning network (e.g., the only-stationary-side resonant LCC 140A), the stationary-side coil (e.g., L₁) current does not depend on the rotor current (Irotor) or the relative position of the stationary-side coils (e.g., L₁) and the rotating-side coil (L₂). As a result, the AC generated at block 1102 (e.g., by the resonant inverter 120A) has an output current root mean square (RMS) value (which would have active and reactive components) that is directly related to the output current of the only-stationary-side tuning network. The resulting high M value and large L_(rotor) inductance, eliminate the need for a rotating-side tuning network. The inductance of the rotating-side inductor (L₂) can be referred or reflected to the stationary-side, and with an appropriate location and sizing of a capacitive component (e.g., the C_(f1) capacitor) of the only-stationary-side tuning network, the rotating-side winding (e.g., L₂) can be tuned from the stationary-side (e.g., through the appropriate location and sizing of the capacitive component (e.g., the C_(f1) capacitor) of the only-stationary-side tuning network). The resulting system 100, 100A is also insensitive to the L_(rotor) inductance because this rotor winding inductance is on the DC side (i.e., downstream from the rectifier 210 shown in FIG. 2 ), and an inductor in steady-state operates as a short circuit under DC voltages and currents. Thus the L_(rotor) only introduces a time-constant when the current changes from one value to another. Other than introducing a time constant (inertia to the change of the current), L_(rotor) is not reflected to the input of the rectifier input 210 and to the stationary-side 220.

Subsequent to the operations at block 1106, the methodology 1100 moves to block 1108. At block 1108, the alternating EMF generated in the rotating-side coil (L₂) generates M between L₁ and L₂, and the rotating-side coil (L₂) uses M to generate AC charging current. At block 1110, the AC charging current is converted to a DC current and provided to downstream motor components (e.g., a rotor, represented in FIG. 2 as L_(rotor) and R_(rotor)).

FIGS. 12-15 depict a more detailed example of a design methodology for determining the component values of the only-stationary-side resonant LCC 140A for the system 100A that eliminates the need for compensation circuitry and/or compensation components on the rotating-side 230. More specifically, FIG. 12 depicts a design methodology 1200 in accordance with embodiments of the disclosure; and FIGS. 13-15 depict equivalent circuits and circuit models (systems 100B, 100C, 100D) used in one or more design methodologies in accordance with embodiments of the disclosure.

Turning to FIG. 12 , the methodology 1200 will be described with reference to some of the component element labels (e.g., L_(f1), C₁, C_(f1), L₁, L₂, etc.) used in the equivalent circuits and circuit models (systems 100B, 100C, 100D) depicted in FIGS. 13-15 . As shown in FIG. 12 , the methodology 1200 is operable to begin, in parallel, at blocks 1202 and 1212 then move through multiple paths to generate the outputs at blocks 1232 (the primary coil current, primary side parallel tuning capacitor current, and the voltage across the primary tuning capacitor), 1236 (output voltage and power), 1222 (design of the primary compensation network according to the value of the primary-side series tuning capacitor (C₁) value). At block 1202, the methodology 1200 calculates the primary coil current, primary side parallel tuning capacitor current, and the voltage across the primary tuning capacitor. At block 1204, the methodology 1200 writes Z_(in) as the sum of Z₁₂ and the inductive reactance of the primary side resonant tuning inductor (L_(f1)). At block 1206, the methodology 1200 writes Z₁₂ as the parallel equivalent impedance of Z_(cf1) and Z₁. In embodiments of the disclosure, Z₁ is the total equivalent impedance seen by the inverter. At block 1208, the methodology 1200 writes Z₁ as the sum of Z_(L1), Z_(c1), and Z_(ref) (Equation-6 in FIG. 8 ), then provides Z₁ to block 1210. Substantially in parallel with the operations at blocks 1202-1208, block 1212 calculates the secondary side (i.e., the rotating-side) reflected impedance Z_(ref) and substitutes it in the Z₁ equation (Equation-6 in FIG. 8 ) at block 1210.

Block 1212 also provides its output to block 1214. At block 1214, the methodology 1200 sums the secondary side's reflected impedance with the primary side coil inductance and the impedance of the series tuning capacitor. At block 1216, the methodology 1200 forms the T network equivalent impedance circuit, calculates branch impedances and the total equivalent impedance seen by the inverter. At block 1218, the methodology 1200 calculates the inverter output current. At block 1220, the methodology 1200 designs the primary side series tuning capacitor value such that the inverter output reactive power is greatly eliminated. Alternatively, block 1220 can tune out the imaginary part of the total equivalent impedance seen by the inverter. At block 1222, the methodology 1222 designs the primary compensation network according to the value of the primary-side series tuning capacitor (C₁) value.

Returning to block 1210, from block 1210, the methodology 1200 moves to block 1230 and calculates Z_(in) that is Z₁ in parallel with Z_(in). The calculation performed in block 1230 is provided to block 1232 and block 1234. At block 1232, the methodology 1200 calculates the primary coil current, the primary side parallel tuning capacitor current, and the voltage across the primary tuning capacitor. At block 1234, the methodology 1200 calculates the secondary side current using voltage induced on the secondary side, along with the total equivalent impedance of the secondary side. The calculations performed at block 1234 are provided to block 1236 where the methodology 1200 calculates the output voltage and power.

Accordingly, it can be seen from the foregoing description of FIGS. 11-15 that the only-stationary-side resonant LCC 140A provides technical effects and technical benefits. Although C₁ is on the stationary-side 230, C₁ performs a rotating-side compensation function operable to provide compensation for the L₂ windings on the rotating-side. This rotating-side compensation function can be accomplished by reflecting the L₂ impedance to the stationary-side 220, then using the various computations shown in FIGS. 8-15 to use the reflected impedance as part of the process to develop the value for C_(f). In some embodiments of the invention, the impedances associated with the primary coils L₂ and the load (as represented by L_(rotor) and R_(rotor) in FIG. 2 ) are reflected to the stationary-side and used to develop the values for C₁. In some embodiments of the disclosure, in addition to compensating for the L₂ windings from stationary-side 220, C₁ also compensates a portion of L or the difference between L₁ and L_(f1), collectively. Thus, in some embodiments of the disclosure, the value of C₁ depends on L₂, L₁ and L₁. C_(f1) is used to “tune out” La. which provides at least a portion of the compensation for the L₁ windings on the stationary-side 220. In embodiments of the invention, rotor winding current prediction module 160 estimates the rotor current without depending on any of the parameter values of L_(f1), C_(f1), and C₁.

The various components/modules of the systems illustrated herein are depicted separately for ease of illustration and explanation. In embodiments of the disclosure, the functions performed by the various components/modules/models can be distributed differently than shown without departing from the scope of the various embodiments of the disclosure describe herein unless it is specifically stated otherwise.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

The diagrams depicted herein are illustrative. There can be many variations to the diagram or the steps (or operations) described therein without departing from the spirit of the disclosure. For instance, the actions can be performed in a differing order or actions can be added, deleted or modified. Also, the term “coupled” describes having a signal path between two elements and does not imply a direct connection between the elements with no intervening elements/connections therebetween. All of these variations are considered a part of the present disclosure.

The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include both an indirect “connection” and a direct “connection.”

The terms “about,” “substantially,” “approximately,” and variations thereof, are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

While the disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. 

What is claimed is:
 1. An electric drive motor system comprising: a stationary-side; a rotating-side; and a stationary-side sensor system operable to detect current on the stationary-side and send current-based sensor readings to a controller; wherein the stationary-side comprises a compensation network; and wherein the controller is operable to perform a rotor current prediction operation comprising predicting a rotor current associated with a rotor of the rotating-side based at least in part on the current-based sensor readings and a parameter of at least one component of the compensation network of the stationary-side.
 2. The electric drive motor system of claim 1, wherein the stationary-side further comprise an inverter operable to convert direct current (DC) received from an energy source to alternating current (AC).
 3. The electric drive motor system of claim 2, wherein the current detected by the stationary-side sensor system comprises the AC.
 4. The electric drive motor system of claim 1 wherein the at least one component of the compensation network of the stationary-side comprises a capacitive element.
 5. The electric drive motor system of claim 1, wherein the at least one component of the compensation network of the stationary-side comprises an inductive element.
 6. The electric drive motor system of claim 5, wherein the at least one component of the compensation network of the stationary-side further comprises a capacitive element.
 7. The electric drive motor system of claim 1, wherein: the compensation network of the stationary-side comprises an only-stationary-side (OSS) compensation network; and the at least one component of the compensation network of the stationary-side comprises a first OSS compensation element of the OSS compensation network.
 8. The electric drive motor system of claim 7, wherein the first OSS compensation element is operable to provide a rotating-side compensation function.
 9. The electric drive motor system of claim 8, wherein a value of the first OSS compensation element is selected to provide the rotating-side compensation function.
 10. The electric drive motor system of claim 1, wherein: the stationary-side comprises a stator having stationary-side windings; the rotating-side comprises the rotor having rotating-side windings; and the stationary-side windings are operable to wirelessly transfer alternating current (AC) excitation signals to the rotating-side windings.
 11. A method of fabricating an electric drive motor system comprising: forming a stationary-side; forming a rotating-side; and forming a stationary-side sensor system operable to detect current on the stationary-side and send current-based sensor readings to a controller; wherein the stationary-side comprises a compensation network; and wherein the controller is operable to perform a rotor current prediction operation comprising predicting a rotor current associated with a rotor of the rotating-side based at least in part on the current-based sensor readings and a parameter of at least one component of the compensation network of the stationary-side.
 12. The method of claim 11, wherein the stationary-side further comprise an inverter operable to convert direct current (DC) received from an energy source to alternating current (AC).
 13. The method of claim 12, wherein the current detected by the stationary-side sensor system comprises the AC.
 14. The method of claim 11 wherein the at least one component of the compensation network of the stationary-side comprises a capacitive element.
 15. The method of claim 11, wherein the at least one component of the compensation network of the stationary-side comprises an inductive element.
 16. The method of claim 15, wherein the at least one component of the compensation network of the stationary-side further comprises a capacitive element.
 17. The method of claim 11, wherein: the compensation network of the stationary-side comprises an only-stationary-side (OSS) compensation network; and the at least one component of the compensation network of the stationary-side comprises a first OSS compensation element of the OSS compensation network.
 18. The method of claim 17, wherein the first OSS compensation element is operable to provide a rotating-side compensation function.
 19. The method of claim 18, wherein a value of the first OSS compensation element is selected to provide the rotating-side compensation function.
 20. The method of claim 11, wherein: the stationary-side comprises a stator having stationary-side windings; the rotating-side comprises the rotor having rotating-side windings; and the stationary-side windings are operable to wirelessly transfer alternating current (AC) excitation signals to the rotating-side windings. 